1. Field of the Invention
This invention relates to a method of olefin hydroformylation and more particularly to a method of olefin hydroformylation in supercritical carbon dioxide resulting in higher yields of the n-isomer.
2. Background of the Invention
Large scale conversion of olefins to aldehydes and/or alcohols is a well-known commercial objective. Conversion of ethylene, propylene, butenes and other alkenes ranging from C.sub.2 -C.sub.13 and C.sub.12 -C.sub.18 to aldehydes and alcohols, for example, is necessary to produce more complex molecules for use as plasticizers, detergents and in a myriad of applications. Such conversions of the alkene can be made using the Oxo process wherein olefins react with carbon monoxide and hydrogen in the presence of a catalyst.
There are problems with the conventional Oxo process, however, such as gas-liquid mixing inefficiencies wherein reactive gases do not adequately mix with each other. Gas-liquid mixing problems lower the yield of the desired n-isomer and limit the upper reaction temperature of the process. For example, typical Oxo processes yield isomer selectivity ratios of approximately 3.0:1 to 4:1, or a 75% to 80% n-isomer yield. R. Fowler, H. Connor and R. A. Baehl. Hydrocarbon Proc. 55(9), 247 (1976). A need exists in the art to increase n-isomer yields significantly as straight chain products are the desired feed stocks for more complex molecule building.
Another significant shortcoming of the Oxo process is the low concentrations of carbon monoxide and hydrogen in the reaction solvent, leading to low catalysts efficiencies and lower overall product yields.
Conventional Oxo processes suffer from yet another shortcoming wherein the separation of catalysts from products involve energy intensive distillations.
A need exists in the art to provide a hydroformylation process wherein gas-liquid mixing problems are minimized, concentrations of synthesis gases in the reaction solvent are maximized, higher ratios of n-isomer to iso-isomers are achieved, and more efficient separation procedures can be utilized for product and catalyst recovery.